Am assuming Thrush and any other causes of vulval itching have been ruled out?
I am guessing you are on the 0.1% estriol cream, which seems to be the standard issue in the NHS. There is another estriol cream available - 0.01% - which gives the same amount of estriol but with a much bigger quantity of cream. The cream is made by a different manufacturer and is very different to the 0.1% variety, containing peanut oil and glycerin, which may be more soothing to the skin. I couldn't tolerate the 0.1% stuff - it burned me - but I love this.
The GP will probably want you to stay on your current regime for a while longer to see if gets better, but if it doesn't improve, it is something else you can ask to try. It's more expensive for them to provide though, so you may have to make a case for trying it.